<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .father {
    height: 400px; background-color: pink; position: relative; padding: 0 200px; }
    .left,.right {
        width: 200px; height: 300px; background-color: yellow; position: absolute; top: 0; }
    .left {
        left: 0; }
    .right {
        right: 0; }
        .center {
        background-color: blue; height: 350px; }
</style>
<body>

    <div class="father">
        <div class="left"></div>
        <div class="center"></div>
        <div class="right"></div>
    </div>
</body>
<script>
    // let arr = [[222, 333, 444], [55, 66, 77] ]
    // // arr += '';
    // arr = arr +''
    // arr = arr.split(',');
    // let a =  Array.isArray(arr)
    // console.log(a);
    // console.log(arr);
    var arr1 = [1, 2, [3, 4]];
    console.log(arr1.flat());

</script>
</html>
